Servicing cell selection in air to ground communication systems

ABSTRACT

Selecting serving cells in air to ground communication systems efficiently and with maximum knowledge of forward and return link channel conditions allows maximum throughput available to a user at any point in time, particularly in the presence of high interference. Airborne based and ground based systems may collect forward and return link channel conditions and develop user capacity estimates to be used by aircraft and ground based transceivers. Such user capacity estimates may be shared among distributed air-to-ground networks to ensure the latest channel conditions are available for serving cell selection decisions.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and the benefit of U.S.Provisional Patent Application No. 62/358,437 entitled “HybridAir-to-Ground Network Incorporating Unlicensed Bands” and filed on Jul.5, 2016, the disclosure of which is hereby incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

The disclosure generally relates to apparatus, methods, and articles ofmanufacture to select serving cells in air to ground communicationsystems and, more particularly, to maximize throughput available to auser of an air to ground communication system in the presence of highinterference.

BACKGROUND

Given the scarcity of allocated radio frequency spectrum, providers ofair-to-ground (ATG) communication systems may make secondary use ofalready allocated spectrum, for example in the 14 gigahertz (GHz) rangeor use unlicensed bands, for example in the 2.4 GHz range, whileproviding ATG services. Unfortunately, radio frequency (RF) spectrumsurveys show that RF noise and interference sources have risen overtime, and are expected to continue to rise in the future. Some examplesurveys of the 2.4 GHz band observed noise rise on the order of 30 dBover a short period of time. Noise surveys also show a non-uniformdistribution of noise levels over time or space. Such high levels ofinterference have the ability to significantly degrade the quality andavailable data bandwidth of the radio link, particularly if theobjective is to provide consistent and reliable data rates that meetcustomer and industry expectations.

Given the presence of high RF noise and/or interference, at a giventime, it is possible to find particular locations where noise orinterference is low enough to guarantee an acceptable data rate. Forexample, for a given aircraft location, establishing a connection withacceptable data rate may utilize a scheme that selects the serving cellconsidering the noise levels from multiple candidate serving celllocations.

Network operators may establish primary communications for controlinformation with the aircraft using their existing equipment andallocated spectrum and use the noisy 2.4 GHz spectrum primarily for datatraffic. Primary in-flight communication networks may require reliableconnectivity between ground and the aircraft, whereas supplementaryin-flight communication networks may operate over noisy radio frequencyspectrum. Some examples of primary networks may include satellitenetworks or other ATG networks that operate over licensed spectrum.

Schemes to select among ATG serving cells that maximize throughput to agiven aircraft in the forward and return directions in a highinterference frequency band may provide significant performanceadvantages in terms of stability of connection, available bandwidth, andlatency

SUMMARY

One exemplary embodiment includes a non-transitory computer readablemedium, comprising processor executable instructions that when executedby a computer processor disposed within an airborne aircraft cause thecomputer processor to command a directional antenna installed on theaircraft and a transceiver disposed within the aircraft to measure afirst signal-to-noise ratio for a first communication channel at a firstlocation on the ground; command the directional antenna and thetransceiver to measure a second signal-to-noise ratio for a secondcommunication channel at a second location on the ground; calculate afirst forward-link user capacity estimate using the firstsignal-to-noise ratio for the first communication channel; calculate asecond forward-link user capacity estimate using the secondsignal-to-noise ratio for the second communication channel; andcalculate a forward-link user capacity matrix using the firstforward-link user capacity estimate and the second forward-link capacityestimate.

Another exemplary embodiment includes a computer-implemented method,executed with a computer processor disposed within an air-to-groundcommunication ground station, that includes commanding, with thecomputer processor, a directional antenna installed at the groundstation and a transceiver disposed within the ground station to measurea first noise power level for a first communication channel at a firstelevation and a first azimuth from a current position of the groundstation; commanding, with the computer processor, the directionalantenna and the transceiver to measure a second noise power level for asecond communication channel at a second elevation and a second azimuthfrom the current position of the ground station; calculating, with thecomputer processor, a first reverse-link user capacity estimate usingthe first noise power level for the first communication channel;calculating, with the computer processor, a second reverse-link usercapacity estimate using the second noise power level for the secondcommunication channel; and calculating, with the computer processor, areverse-link user capacity matrix using the first reverse-link usercapacity estimate and the second reverse-link capacity estimate.

Yet another exemplary embodiment includes a computer system comprisingone or more processors and/or transceivers configured to retrieve atleast one of (i) a forward-link user capacity matrix comprising aplurality of forward-link user capacity estimates each associated with alocation on the ground; and (ii) a return-link capacity matrixcomprising a plurality of reverse-link user capacity estimates eachassociated with an azimuth and elevation from a current location of anairborne aircraft; calculate a candidate serving cell, using at leastone of (i) the forward-link user capacity matrix and (ii) thereverse-link user capacity matrix; and command a directional antenna anda transceiver to transmit or receive data with the candidate servingcell.

Exemplary embodiments may include computer-implemented methods that mayin other embodiments include apparatus configured to implement themethod, and/or non-transitory computer readable mediums comprisingcomputer-executable instructions that cause a processor to perform themethod.

Advantages will become more apparent to those skilled in the art fromthe following description of the preferred embodiments which have beenshown and described by way of illustration. As will be realized, thepresent embodiments may be capable of other and different embodiments,and their details are capable of modification in various respects.Accordingly, the drawings and description are to be regarded asillustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The Figures described below depict various aspects of the system andmethods disclosed herein. It should be understood that each figuredepicts an aspect of a particular aspect of the disclosed system andmethods, and that each of the Figures is intended to accord with apossible aspect thereof. Further, wherever possible, the followingdescription refers to the reference numerals included in the followingFigures, in which features depicted in multiple Figures are designatedwith consistent reference numerals.

There are shown in the Figures arrangements which are presentlydiscussed, it being understood, however, that the present embodimentsare not limited to the precise arrangements and instrumentalities shown,wherein:

FIG. 1 illustrates an exemplary illustration of an air-to-groundcommunication system, including a variety of ground stationscommunicating with an airborne aircraft, in accordance with one aspectof the present disclosure;

FIG. 2 illustrates an exemplary block diagram of a method to communicatebetween a variety of ground stations and an airborne aircraft, inaccordance with one aspect of the present disclosure;

FIG. 3 illustrates an exemplary block diagram of a system that includesa variety of geographically distributed ground stations interconnectedwith ground station controllers, that communicate with an airborneaircraft, in accordance with one aspect of the present disclosure;

FIG. 4 illustrates an exemplary block diagram of a system that includesa variety of geographically distributed ground stations that communicatewith an airborne aircraft, where the aircraft builds a forward-link usercapacity matrix, in accordance with one aspect of the presentdisclosure;

FIG. 5 illustrates an exemplary illustration of a forward-link usercapacity matrix, in accordance with one aspect of the presentdisclosure;

FIG. 6 illustrates an exemplary block diagram of a system that includesa variety of geographically distributed ground stations that communicatewith an airborne aircraft, where the ground stations build areverse-link noise matrix and reverse-link user capacity matrix, inaccordance with one aspect of the present disclosure;

FIG. 7 illustrates an exemplary illustration of a reverse-link noisematrix, in accordance with one aspect of the present disclosure;

FIG. 8 illustrates an exemplary illustration of a reverse-link usercapacity matrix, in accordance with one aspect of the presentdisclosure;

FIG. 9 illustrates an exemplary block diagram of a computing system, inaccordance with one aspect of the present disclosure; and

FIG. 10 illustrates an exemplary non-transitory computer readablemedium, in accordance with one aspect of the present disclosure.

The Figures depict preferred embodiments for purposes of illustrationonly. Alternative embodiments of the systems and methods illustratedherein may be employed without departing from the principles of theinvention described herein.

DETAILED DESCRIPTION

Although the following text sets forth a detailed description ofnumerous different embodiments, it should be understood that the legalscope of the description is defined by the words of the claims set forthat the end of this patent and equivalents. The detailed description isto be construed as exemplary only and does not describe every possibleembodiment since describing every possible embodiment would beimpractical. Numerous alternative embodiments may be implemented, usingeither current technology or technology developed after the filing dateof this patent, which would still fall within the scope of the claims.

In one embodiment, aircraft air-to-ground (ATG) communication equipmentperforms power measurements across an allocated or unallocated operatingfrequency bandwidth using a high directivity antenna steered in thedirections of the ATG stations. This procedure may end with the creationof a prioritized list of candidate forward link (FL) serving cells alongwith their corresponding SINR levels at different frequency sub-bands,or communication channels.

The ground stations may also perform periodic power measurements acrossthe operating frequency in different directions using steerable highdirectivity antennas. Such a procedure may end with the characterizationof the return link (RL) noise at different frequency sub-bands ondifferent directions, and the creation of a RL noise matrix. The groundstations may then forward the RL noise matrix to the Ground Station (GS)ATG network controller, for example in a centralized implementation, orto all neighbor ground stations, for example in a distributedimplementation.

In embodiments where the aircraft is ready to access a supplementaryin-flight communication (IFC) system, the aircraft may send thecandidate FL serving cell list and its location information to the ATGnetwork controller over the primary IFC network.

The ATG network controller may receive the candidate FL serving celllist and begin antenna resource allocation in a predetermined orcalculated order of priority. Once allocation is successful, thecorresponding serving cell may steer a FL beam towards the known orcalculated aircraft location, and thus the UE, or aircraft, is now readyfor FL transmission. Subsequently, the ground station controller, usingthe location information from the aircraft and the RL noise matrix, maygenerate or calculate a prioritized list of RL candidate serving cellsin a listing or order of priority. Following the successful creation ofthis list, the network controller may begin resource allocationprocedures attempts in order of priority. Once the RL allocation issuccessful, the corresponding serving cell may steer a RL beam towardthe aircraft, and the UE is now ready for RL transmissions.

In one embodiment the air interface technology may require the FL and RLserving cells to be the same, and thus the ground station controller maydetermine a cell where the FL and RL meet certain data rate criteria.

By employing a high directivity antenna to measure the noise levels inmany different possible directions of communication and refreshing suchinformation periodically, the ATG supplementary IFC network may selectserving cells that provide the best available SINR. Such an embodimentensures that the aircraft will always be served by the cell thatprovides the best possible data rate to an aircraft.

The use of a high reliability out-of-band link between the aircraft UEand the GS network allows communication of the noise measurements,channel status information, and location information for the purpose ofselecting a suitable serving cell and aligning a steerable antenna thattracks the aircraft. In one embodiment, use of the out-of-band channelenables identification of the best server and antenna steering.

One embodiment includes a scheme that uses short term power measurementswith steerable directive antennas on the aircraft to identify theserving cell in the direction with the highest SINR. A FL User CapacityMatrix may be built, for example, based on SINR measurements in thedirection of all possible servers.

Another embodiment includes short and long term power measurements withsteerable directive antennas on the ground station to create threedimensional noise plus interference characterization matrix and a cellbarring matrix with the objective of identifying serving cells with thelowest RL noise rise. Such an embodiment includes a RL Noise Matrix as athree dimensional characterization of the RL to enable quickidentification of the most effective RL serving cell.

Yet another embodiment includes a method to perform FL and RL servingcell selection based on noise characterization provided by the UE, oraircraft, in a centralized or distributed manner. Such an embodiment mayinclude use of FL and RL User Capacity matrix to enable identificationof the FL and RL metric that meets any desired selection criteria and issuitable for a centralized or distributed processing implementation.

The following terms may include their associated definitions as statedbelow, in accordance with the present disclosure:

Primary IFC network: the network that provides the primary IFC link tothe aircraft. This network provides a reliable connection betweenaircraft and ground networks.

ATG: Air to Ground System that provides supplemental IFC connectivityusing noisya spectrum or uses spectrum as secondary use.

Primary GSC: Gateway of the primary IFC network. If the Primary IFCnetwork is an ATG system, this can be defined as the Primary GroundStation Controller. If the Primary IFC network is a satellite system,this can be a teleport.

PGS: fixed stations of the Primary IFC network. If the Primary IFCnetwork is an ATG system, these can be defined as the Primary GroundStations. If the Primary IFC network is a satellite system, these wouldbe the transponders.

GSC: Ground station controller of the supplementary IFC system. This isalso known as the ATG Ground Station Controller. If the ATG system usesa distributed implementation, the GSC only performs routing of controlplane messages. Otherwise if the implementation is centralized, itperforms some computation and decision functions that are part of theantenna resource allocation procedures.

GS: Ground stations of the supplementary IFC system. These are alsoreferred as base stations. The area of coverage of a ground station canbe divided into cells to increase spectral reuse and to allow practicaldeployment of beam forming technology. This includes the highdirectivity steerable antennas or antenna beams. A GS may have one ormore antenna beams per cell.

Aircraft or UE: ATG mobile equipment that is installed in the aircraft.This includes modem and the high directivity steerable antennas orantenna beams for the ATG system.

Forward link: radio link for wireless transmission from the GS to theUE.

Return link: radio link for wireless transmission from the UE to the GS.

In-band transmission: transmission using the noisy frequency band (e.g.unlicensed spectrum).

Out-of-band transmission: transmission using a licensed band thatguarantees good reliability

ATG OOB Control: ATG signaling messages exchanged out-of-band betweenthe UE and the GS or GSC.

GPS Information: the set of information that includes: latitude,longitude, altitude, heading and speed of the aircraft.

Turning to the exemplary air-to-ground communication system 100illustrated in FIG. 1, an aircraft 110 may include a transceiver 112 andantenna 113 to communicate with a number of ground stations 120, 135,150, and 165, geographically dispersed from one another. Each groundstation 120, 135, 150, and 165 may include a respective ground stationtransceiver 125, 140, 155, and 160 to transmit and receive signals. Forexample, ground station 150 with ground station transceiver 155 maycommunicate a radio frequency signal 145 to the with the antenna 113 andtransceiver 112 on the aircraft 110.

Likewise for each ground station 125, 140, and 170, each withincommunication range of the aircraft 110, RF signals 115, 139, and 160may be transmitted between the ground stations and the aircraft antenna113 and transceiver 112. Each of the ground stations 125, 140, 155, and170 may be disposed a different physical distances from the aircraft110, and experience differing path attenuation, local area interferenceand noise, etc. that interfere with transmission of the signals 115,130, 145, and 160 in differing ways. However, in some embodiments, thedata services provided by the aircraft transceiver 112 may require useof some or all of the ground stations, or a changing set of the groundstations as channel conditions change.

For example, in the illustrated block diagram 200 of FIG. 2, serving andneighbor ground stations and aircraft stations use a method to measureand use changing channel conditions to ensure reliable data services.The serving ground station may measure power levels in variousdirections (block 205) and build a return link noise matrix (block 210)using the results of such measurements. Likewise, a neighbor groundstation may measure power levels in various directions (block 225) andbuild a return link noise matrix (230) using the results. In oneembodiment, both the serving and neighbor ground stations may share thereturn link noise matrices with a centralized controller, or with otherneighbor ground stations (blocks 215 and 235).

In some embodiments, the aircraft station may measure power levels inthe direction of the serving and neighbor ground stations (block 240).The aircraft station may calculate or determine forward link candidateserving stations and record SINR measurements in for example a forwardlink user capacity matrix and transmit such candidates to a networkcontroller (block 250). The aircraft station (block 255) and servingground station allocated by the network controller based on the noisematrix (block 220) may steer a communications beam towards the aircraft,and communicate over forward and return links. As such, the mosteffective ground station communicates with the aircraft station asdetermined by knowledge of the forward and return link channelconditions.

Effective Use of Forward-Link and Return-Link Data

FIG. 3 illustrates an exemplary system with interconnected groundstations 315, 320, 370, 330, and 335, and ground station controllers 305and 310 communicating with an airborne aircraft, or UE 340. A variety ofprimary ground stations (PGS) 315 and 325 are connected to the primaryground station controller (GSC) 305 by communication links 365 and 375.Likewise a variety of ground stations (GS) 320 and 325 are connected tothe ground station controller (GSC) 310 by communication links 340 and345. The primary GSC 305 may be connected by a communication link 307 tothe GSC 310.

The UE, or aircraft 340, may in some embodiments send an AntennaResource Request 350 message to the GSC 310 over the Primary IFC link370. The message may include the FL User Capacity Matrix sorted byforward-link data rate (FR). The UE 340 also may begin sending the GPSinformation periodically to the GSC 310. Depending on whether acentralized or distributed embodiment is employed, the GSC 310 mayexecute most of the serving cell antenna resource allocation proceduresor act as a signaling layer proxy between the UE 340 and the GSs.

In the centralized case, the GSC 310 parses the GSC message and selectsthe GS with the highest FR, then sends a FL Antenna Allocation Request350 message along with the GPS information. The GS, for example 320 uponsuccessful allocation of antenna resources respond with a FL AntennaAllocation Accept message and starts tracking the aircraft. Note thatthe GSC 310 continues forwarding the periodic GPS information to the GSto allow continuous tracking of the aircraft. If the GS is not able toallocate antenna resources to the aircraft, it responds with a FLAntenna Allocation Reject. Then the GSC 310 selects the GS with thesecond highest FR and the process repeats. After completion the GSC 310sends an OOB indication 350 to the UE 340 signaling that the FL antennaallocation is complete.

In parallel or sequentially, the GSC 310, using the GPS information,creates a list of candidate RL serving cells based on free space losscharacteristics only. Then, for each candidate cell, the azimuth fromthe cell to the UE 340 is determined, if the GS supports steering of thebeam 355 in elevation, the elevation angle is also determined. With theazimuth and elevation information and its corresponding RL Noise Matrixthe RL Noise plus interference for each sub-band is obtained. The GSC310 calculates distance between the UE 340 and the candidate servingcell based on UE 340 and GS GPS information. Given the distance to theUE 340, the RL power capabilities of the UE and the RL Noise plusinterference the GSC can estimate the RL data rate (RR) for eachsub-band and the total maximum RL data for each candidate serving cell.

The RL User Capacity Matrix captures the maximum data rate the candidateGSs can deliver, for example over the ATG link 360. Similar to the FLcase, the GSC performs resource allocation procedures for the RL.Starting from the cell with the highest RR, the GSC attempts to allocateantenna resources by sending a RL Antenna Allocation Request 350. Uponsuccessful setup of RL resources the GSC sends confirmation to the UE,at this point the UE is ready to receive RL data over the ATG link.

In the distributed case, the GSC 310 sends an Antenna Allocation Requestmessage 350 along with FL User Capacity Matrix and the GPS informationto the GS with the highest FR, this is referred to as the anchor GS. Theanchor GS 320 attempts to secure FL antenna resources, if this fails, itsends a FL Antenna Allocation Request and the last GPS information tothe GS with the second highest FR. This process continues until FLantenna resources are secured. In parallel, RL antenna resources aresecured in the same way, for example by steering the beam 355 towardsthe UE 340. Since anchor GS 320 has the RL Noise Metric of all neighborcells, it can perform RL antennal allocation procedures in the same way.Upon successful setup of FL and RL allocation, the anchor GS 320 sendsan Antenna Allocation Accept to the GSC 310 which includes theidentification of the GS 320 where resources were allocated. The GSCchanges the delivery of the periodic GPS information to the GS 320 whereresources were setup and notifies the UE 340 over the OOB link 350 thatFL and RL antenna resources had been allocated. After this the UE 340 isready to exchange data over the ATG network.

In some embodiments, the air interface technology may require the FL andRL serving cell to be the same. In that case, the selection of the FLand RL serving cell cannot be done independently since it is possiblethat the cell that provides the highest FL data rate does not offer thehighest RL data rate, or could even offer the worse RL data rate.Therefore, additional criteria such as the current UE RL and FL traffictype and loading and the anticipated traffic type and loading for theATG network, need to be introduced to select the FL and RL servingcells. The exact criteria may depend on the type of traffic the ATG isexpected to carry. In one embodiment, candidate serving cells that meetminimum thresholds for both RL and FL data rates could be identified,and then one of those selected as serving cell based on either highestRL or highest FL data rate. In the general case of TCP type traffic, theFL and RL bandwidth requirement may not be symmetric. For example,analysis of some traffic pattern in IFC services show that the ratiobetween RL and FL offer load is about 1:7. Then a possible embodimentcould be to identify all cells that offer RL to FL data rate ratiogreater than a given threshold and then sort this list in descendingorder of FR. The GSC or the anchor GS attempts to secure FL and RLantenna resources starting from the cell with the highest FR.

After successful setup of FL and RL serving cell antenna resources theUE can perform access procedures on the air interface following theprocedures defined for the corresponding air interface technology. Notethat GPS information is continuously sent to the ATG network over thePrimary IFC link, this enables antenna steering to track the aircraft.Once the UE gains access to the ATG network it can continue updating theFL User Capacity Matrix taking measurements during silence periods orusing a second antenna. When the SINR degrades below a certain thresholdor better candidates are found, the UE sends a Handover Request message,which includes the FL User Capacity Matrix, to the GSC. This enablesmobility throughout the ATG network.

In an alternative embodiment, the GSC, centralized implementation, or GSsites, distributed implementation, use GPS Information of each aircraftprovided via the OOB control channel. With this information the GSC orGS sites can estimate the current elevation and azimuth angle andprojected path or heading for each aircraft. The ATG network may usethis information to surgically update the RL Noise Matrices by steeringantennas to make noise plus interference measurements at the currentaircraft location and at the projected aircraft locations in the future.

Forward-Link User Capacity Characterization

An exemplary system 400 illustrated in FIG. 4 to collect and calculateforward link user capacity includes a primary GSC 405 connected to a GSC410 through a communication link 415. A set of primary ground stations420 and 425 are connected to the primary GSC 405 by communication links430 and 435. Likewise a set of ground stations 440 and 445 are connectedby communication links 455 and 460 to the GSC 410. The aircraft, or UE470 communicates with three ground stations 440, 445, and 450 viawireless communication links 475, 480, and 485.

The UE 470 starts the process of accessing the ATG network by estimatingSINR for each surrounding cell, for example 440, 445, and 450. This canbe performed by making SINR measurements or by measuring noise plusinterference and deriving the SINR based on the power settingsconfigured for the corresponding cell. In the former case, the UE 470needs to know the times when each candidate serving cell pilot signal istransmitted to enable SINR measurements, therefore time synchronizationwith each candidate serving cell may be necessary. To address thisproblem, prior to start the power measurements the UE 470 sends apre-allocation message to the GSC 410 over the Primary IFC link, asillustrated in FIG. 3, this message contains the GPS information for theaircraft. The GSC 410 forwards this messages to a number of cellssurrounding the aircraft, for example 440, 445, and 450. Upon receptionof the pre-allocation message, the cells bring up a FL beam, for example475, 480, and 485, in the direction of the aircraft and startstransmission of pilot signals. Using the pilot signals the UE 470performs time synchronization followed by SINR measurements for eachcandidate serving cell 440, 445, and 450. Once the FL antenna resourcesis complete, the beams are brought down.

Alternatively, the UE 470 can estimate the SINR based on noise plusinterference measurements and the power settings of each candidateserving cell 440, 445, and 450. This approach is simpler to implementhowever it has stricter requirements on the antennas. Specifically, thisapproach may work well if the GS FL beams are narrow enough so that theprobability of two aircrafts being served by the same cell is very low.The UE 470 may steer its narrow beam directional antenna pointing toeach neighboring cell to enable the measurements. The UE 470 may knowthe location and basic configuration of all cells in the ATG network,this is configured during UE provisioning or downloaded over the PrimaryATG network after provisioning. Because the FL transmission beam isnarrow and the GS is not transmitting in the direction of the aircraft,all the measured power is expected to be noise plus interference only.This measurement will give the denominator for the SINR calculation. Thesignal power is estimated based on the known power level of thecandidate serving cell adjusted by propagation losses. The propagationloss can be derived from the distance between the aircraft and the GS.With that information, the SINR is estimated.

In some embodiments the SINR measurements or estimations are performedat different sub-bands of the operational bandwidth. With thatinformation, the UE 470 estimates the expected FL data rate (FR) foreach candidate serving cell, and builds a FL User Capacity Matrix. Anexemplary illustration of a FL User Capacity Matrix is shown in FIG. 5.In exemplary embodiment, the bandwidth B is divided into N sub-bands(e.g. SB1, SB2, SBN) 505. Furthermore, the matrix 500 depicts the casewhere expected data rate for S ground stations (e.g. GS1, GS2, GSS) 510is characterized. Using the SINR at each sub-band and the spectralefficiency vs SINR for the air interface technology in use the UE canestimate the expected data rate for each sub-band and the total expecteddata rate for each GS (e.g. FR1, FR2, FRS) 515. The FR is a singlemetric that accounts for the SINR and the total available bandwidth,this number can be used as the figure of merit to identify the servingcell that can provide the highest FL throughput. Once the UE 470completes the creation of the FL User Capacity Matrix 500 it is ready toaccess the ATG system.

Return-Link User Capacity Characterization

One exemplary system 600 to determine return-link capacity isillustrated in the block diagram of FIG. 6. The system 600 includes aprimary GSC 605 connected to a GSC 610 through a communication link 615.A set of primary ground stations 620 and 625 are connected to theprimary GSC 605 by communication links 645 and 650. Likewise a set ofground stations 630, 635, and 640 are connected by communication links655, 660, and 665 to the GSC 610.

To obtain high SINR levels, good spatial isolation is needed in theradio link, enabled by using high directivity antennas with narrowbeamwidths and steerable capabilities in order to track the aircraft. Inone embodiment, the elevation plane pattern of the antenna can beconstant and optimized to provide good coverage in elevation, then theazimuth antenna beamwidth should be narrow enough to reduce interferencein the azimuth plane. In this case, an azimuth beamwidth of 10 degreesor less could be used. If the antenna technology allows to form a pencilbeam, for example the beams 670, 675, and 680, then a beamwidth inazimuth and elevation of 10 degrees or less could be used. Thisinvention does not define the exact beamwidth since that would depend onthe specific link budgets, levels of interference and antenna technologyavailable.

The GSs 630, 635, and 640 periodically measures the RL noise plusinterference levels. If frequency division duplexing is used,measurements can be performed at any time the RL is not used, or byscheduling silence periods. Otherwise, if time division duplexing isused, measurements can be performed any time the RL is not used or byusing the guard time period. Power measurements are used to estimate theRL noise power. Considering that the GS controls the FL and RLscheduling, RL power measurements performed when no transmissions areexpected represent only noise and interference power. The entire RLnoise plus interference power characterization is captured in a RL NoiseMatrix 700, as illustrated in FIG. 7.

The RL Noise Matrix 700 is a three dimensional characterization of theRL noise plus interference. The bandwidth B is divided in N sub-bands(e.g. SB1, SB2, SBN) 705, the value of N would depend on many factorslike resource allocation bandwidth, channel state reporting bandwidth,measurement speed, etc. The area of coverage in azimuth plane is dividedinto M different directions (e.g. Az1, Az2, . . . , AzM) 720 accordingto the azimuth beamwidth of the antenna array. For example, if a sectoris intended to cover 60° and the azimuth beamwidth is 10°, then M is 6and the azimuth directions would be ±5, ±15, ±25 (assuming 0° is at thecenter of the sector). Similarly, the elevation plane is divided into Ldifferent elevations (E1, E2, . . . , EL) 715 according to the elevationbeamwidth. For example, if the sector is intended to cover elevationsfrom 0° to 40° and the elevation beamwidth is 10°, then L is 4 and theelevation directions are 5, 15, 25 and 35. In total the antenna beam issteered across MxL different directions and on each direction noise plusinterference is measured for each of the N sub-bands. The objective isto characterize the noise across the degrees of freedom as the resourceallocation will take place. In this document a given sub-band, azimuthand elevation combination is referred as the frequency-space resource.For the case where the antenna is not steerable in the elevation planeand rather has an elevation pattern that allows enough coverage inelevation, the RL Noise Matrix reduces to a two dimensional matrix.

The simplest way to iterate through all frequency-space resources is around robin scheme. However other schemes can be depicted to better fitthe spatial multiplexing scheduling demands. For example, a weightingscheme where azimuths or elevations with more usage are assigned higherweights and therefore measured more often can be used. Anotheralternative is to update the RL noise matrix based on the knowntrajectories of scheduled flights.

For each frequency-space resource the RL Noise matrix captures theaverage noise and interference power. The timescales of the variabilityin interference and implementation constraints define the time durationover which to perform the power average. For the RL Noise matrix theaverage window is expected to be short term. There could also be otherfactors that make a certain frequency-space resource unsuitable to use,especially when observed over a long term window. For example, highnoise peaks that cause the link to drop often with erratic patterns, inthose cases it is better to bar that frequency-space resource fromusage. This condition can be captured by another matrix named RL NoiseBarring Matrix. The objective of this matrix is to avoid a given cell tobe assigned as a server on a given frequency-space if there is a highprobability that the noise conditions will significantly degrade thelink. Therefore long term observations define the RL Noise BarringMatrix. Additionally, it could make more sense to bar an azimuthdirection all together, in this case an additional barring flag 710 perazimuth can be added to the RL Noise Matrix.

Once the RL Noise matrix 700 is complete, the GSs send it periodicallyto the GSC 610, centralized implementation case; or sends it to all itsneighbors, distributed implementation case. Note that the RF Noisematrix 700 is continuously updated, in this way the GSC 610 or theneighbor GSs always have the latest information.

Similar to the FL User Capacity Matrix 500 of FIG. 5, The RL UserCapacity Matrix 800 illustrated in FIG. 8 captures the maximum data rate(RR) 815 the candidate GSs 810 can deliver, for example over the ATGlink 360 of FIG. 3. In exemplary embodiment, the bandwidth B is dividedinto N sub-bands (e.g. SB1, SB2, SBN) 805. Similar to the FL case, theGSC 610 performs resource allocation procedures for the RL. Startingfrom the cell with the highest RR, the GSC 610 attempts to allocateantenna resources by sending a RL Antenna Allocation Request 350 asillustrated in FIG. 3. Upon successful setup of RL resources the GSC 610sends confirmation to the UE, at this point the UE is ready to receiveRL data over the ATG link.

Alternative Data Use and Characterization Embodiments

Alternative embodiments of the present disclosure includecharacterization of the noise and interference environment relying onthe spatial isolation provided by directivity nature of the antennas.Such an embodiment differs from existing technologies that rely onpredefined coverage footprints defined by a wide broadcast beam todetermine the serving cell.

Furthermore, existing technologies fail to select a serving cellfollowing comparison of data rates derived from measured noise atdifferent sub-bands and spatial directions. The use of an OOB link toenable beamforming makes the ATG system more robust to interference andenables completion of the serving cell setup process with additionalimmunity to interference in the ATG spectrum.

Other embodiments include selecting the best server making use ofcapabilities of narrow beam antenna technology and exploiting thespatial diversity that an ATG network creates around the aircraft. Suchan embodiment enables full use of all degrees of freedom available forresource allocation and therefore identifies the best possible server.

Still other embodiments include multiple static beams that allow theaircraft to perform access procedures in the noisy spectrum. However,such an embodiment does not guarantee that the serving cell provides thebest possible throughput and reliable link. Furthermore, a large numberof beams may be required to provide sufficient coverage.

Yet another alternative embodiment includes sending the GPS informationover an OOB link, but leaving all the other control messages in-band.One aspect includes configuring a wide broadcast beam on each cell toperform FL SINR measurements. Furthermore, this embodiment may provideadvantages for the case where the FL and RL need to be served by thesame cell.

In some embodiments an 800 MHz ATG network may serve as the Primary IFClink and a 2.4 GHz ATG LTE network may serve as a supplemental service.However, in other embodiments IFC solutions may operate over LEOsatellite constellations when available. LEO links may provide lowenough latency to serve as an OOB link to enable exchange of controlinformation to support the configuration of steerable beams between theaircraft and the ATG network.

Still more embodiments may include technologies other than LTE. Forexample, air interface technologies that allow supplementing the datapipe in only one direction, for example DVB, can be used and theinformation to enable tracking of the aircraft with a steerable beam canbe sent over a reliable OOB connection.

FIG. 9 illustrates an exemplary computing system 900, for example thatmay in some embodiments correspond to one or more GSCs, GS, and UE ofFIGS. 1, 3, 4 and 6, or otherwise, that includes one or moremicroprocessors 905, coupled to supporting devices through multi-accessbusses 925 and 940. Dynamic random access memory 930 and 935 mayinterface to data bus 925, and store data used by the one or moremicroprocessors 905. The system 900 includes instruction registers 920that store executable instructions for the one or more microprocessors905, and data registers 915 that store data for execution. In someembodiments, the system 900 includes one or more arithmeticco-processors 910, to assist or supplement the one or moremicroprocessors 905. Data bus 940 includes interfaces to a graphicsinterface 945 that may in some embodiments process and transmitgraphical data for a user on a display or similar devices. Likewise,data bus 940 includes interfaces for a digital I/O interface thatprocesses and transmits, for example, keyboard, pointing device, andother digital and analog signals produced and consumed by users or othermachines. A network interface 955 processes and transmits encodedinformation over wired and wireless networks to connect the system 900to other machines and users. Data bus 940 also includes at least oneinterface to a non-volatile memory interface, that may process andtransmit data that resides on non-volatile memory devices.

FIG. 10 illustrates a non-transitory computer readable medium 1005, thatcomprises processor executable instructions 1010. Such processorexecutable instructions may include instructions executed by the one ormore microprocessors 905 of FIG. 9.

Additional Considerations

All of the foregoing computer systems may include additional, less, oralternate functionality, including that discussed herein. All of thecomputer-implemented methods may include additional, less, or alternateactions, including those discussed herein, and may be implemented viaone or more local or remote processors and/or transceivers, and/or viacomputer-executable instructions stored on computer-readable media ormedium.

The processors, transceivers, mobile devices, service terminals,servers, remote servers, database servers, heuristic servers,transaction servers, and/or other computing devices discussed herein maycommunicate with each via wireless communication networks or electroniccommunication networks. For instance, the communication betweencomputing devices may be wireless communication or data transmissionover one or more radio links, or wireless or digital communicationchannels.

Customers may opt into a program that allows them share mobile deviceand/or customer, with their permission or affirmative consent, with aservice provider remote server. In return, the service provider remoteserver may provide the functionality discussed herein, includingsecurity, fraud, or other monitoring, and generate recommendations tothe customer and/or generate alerts for the customers in response toabnormal activity being detected.

The following additional considerations apply to the foregoingdiscussion. Throughout this specification, plural instances mayimplement components, operations, or structures described as a singleinstance. Although individual operations of one or more methods areillustrated and described as separate operations, one or more of theindividual operations may be performed concurrently, and nothingrequires that the operations be performed in the order illustrated.Structures and functionality presented as separate components in exampleconfigurations may be implemented as a combined structure or component.Similarly, structures and functionality presented as a single componentmay be implemented as separate components. These and other variations,modifications, additions, and improvements fall within the scope of thesubject matter herein.

Additionally, certain embodiments are described herein as includinglogic or a number of routines, subroutines, applications, orinstructions. These may constitute either software (e.g., code embodiedon a machine-readable medium or in a transmission signal) or hardware.In hardware, the routines, etc., are tangible units capable ofperforming certain operations and may be configured or arranged in acertain manner. In example embodiments, one or more computer systems(e.g., a standalone, client or server computer system) or one or morehardware modules of a computer system (e.g., a processor or a group ofprocessors) may be configured by software (e.g., an application orapplication portion) as a hardware module that operates to performcertain operations as described herein.

In various embodiments, a hardware module may be implementedmechanically or electronically. For example, a hardware module maycomprise dedicated circuitry or logic that is permanently configured(e.g., as a special-purpose processor, such as a field programmable gatearray (FPGA) or an application-specific integrated circuit (ASIC)) toperform certain operations. A hardware module may also compriseprogrammable logic or circuitry (e.g., as encompassed within ageneral-purpose processor or other programmable processor) that istemporarily configured by software to perform certain operations. Itwill be appreciated that the decision to implement a hardware modulemechanically, in dedicated and permanently configured circuitry, or intemporarily configured circuitry (e.g., configured by software) may bedriven by cost and time considerations.

Accordingly, the term “hardware module” should be understood toencompass a tangible entity, be that an entity that is physicallyconstructed, permanently configured (e.g., hardwired), or temporarilyconfigured (e.g., programmed) to operate in a certain manner or toperform certain operations described herein. Considering embodiments inwhich hardware modules are temporarily configured (e.g., programmed),each of the hardware modules need not be configured or instantiated atany one instance in time. For example, where the hardware modulescomprise a general-purpose processor configured using software, thegeneral-purpose processor may be configured as respective differenthardware modules at different times. Software may accordingly configurea processor, for example, to constitute a particular hardware module atone instance of time and to constitute a different hardware module at adifferent instance of time.

Hardware modules may provide information to, and receive informationfrom, other hardware modules. Accordingly, the described hardwaremodules may be regarded as being communicatively coupled. Where multipleof such hardware modules exist contemporaneously, communications may beachieved through signal transmission (e.g., over appropriate circuitsand buses) that connect the hardware modules. In embodiments in whichmultiple hardware modules are configured or instantiated at differenttimes, communications between such hardware modules may be achieved, forexample, through the storage and retrieval of information in memorystructures to which the multiple hardware modules have access. Forexample, one hardware module may perform an operation and store theoutput of that operation in a memory device to which it iscommunicatively coupled. A further hardware module may then, at a latertime, access the memory device to retrieve and process the storedoutput. Hardware modules may also initiate communications with input oroutput devices, and may operate on a resource (e.g., a collection ofinformation).

The various operations of example methods described herein may beperformed, at least partially, by one or more processors that aretemporarily configured (e.g., by software) or permanently configured toperform the relevant operations. Whether temporarily or permanentlyconfigured, such processors may constitute processor-implemented modulesthat operate to perform one or more operations or functions. The modulesreferred to herein may, in some example embodiments, compriseprocessor-implemented modules.

Similarly, the methods or routines described herein may be at leastpartially processor-implemented. For example, at least some of theoperations of a method may be performed by one or more processors orprocessor-implemented hardware modules. The performance of certain ofthe operations may be distributed among the one or more processors, notonly residing within a single machine, but deployed across a number ofmachines. In some example embodiments, the processor or processors maybe located in a single location (e.g., within a home environment, anoffice environment or as a server farm), while in other embodiments theprocessors may be distributed across a number of locations.

The performance of certain of the operations may be distributed amongthe one or more processors, not only residing within a single machine,but deployed across a number of machines. In some example embodiments,the one or more processors or processor-implemented modules may belocated in a single geographic location (e.g., within a homeenvironment, an office environment, or a server farm). In other exampleembodiments, the one or more processors or processor-implemented modulesmay be distributed across a number of geographic locations.

Unless specifically stated otherwise, discussions herein using wordssuch as “processing,” “computing,” “calculating,” “determining,”“presenting,” “displaying,” or the like may refer to actions orprocesses of a machine (e.g., a computer) that manipulates or transformsdata represented as physical (e.g., electronic, magnetic, or optical)quantities within one or more memories (e.g., volatile memory,non-volatile memory, or a combination thereof), registers, or othermachine components that receive, store, transmit, or displayinformation.

As used herein any reference to “one embodiment” or “an embodiment”means that a particular element, feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment.

Some embodiments may be described using the expression “coupled” and“connected” along with their derivatives. For example, some embodimentsmay be described using the term “coupled” to indicate that two or moreelements are in direct physical or electrical contact. The term“coupled,” however, may also mean that two or more elements are not indirect contact with each other, but yet still co-operate or interactwith each other. The embodiments are not limited in this context.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

In addition, use of the “a” or “an” are employed to describe elementsand components of the embodiments herein. This is done merely forconvenience and to give a general sense of the description. Thisdescription, and the claims that follow, should be read to include oneor at least one and the singular also includes the plural unless it isobvious that it is meant otherwise.

The patent claims at the end of this patent application are not intendedto be construed under 35 U.S.C. §112(f) unless traditionalmeans-plus-function language is expressly recited, such as “means for”or “step for” language being explicitly recited in the claim(s).

The systems and methods described herein are directed to improvements tocomputer functionality, and improve the functioning of conventionalcomputers.

This detailed description is to be construed as exemplary only and doesnot describe every possible embodiment, as describing every possibleembodiment would be impractical, if not impossible. One may be implementnumerous alternate embodiments, using either current technology ortechnology developed after the filing date of this application.

What is claimed is:
 1. A non-transitory computer readable medium,comprising processor executable instructions that when executed by acomputer processor disposed within an airborne aircraft cause thecomputer processor to: command a directional antenna installed on theaircraft and a transceiver disposed within the aircraft to measure afirst signal-to-noise ratio of a first communication channelcorresponding to a first location on the ground, the first communicationchannel configured to support transmissions to/from the airborneaircraft; command the directional antenna and the transceiver to measurea second signal-to-noise ratio of a second communication channelcorresponding to a second location on the ground, the secondcommunication channel configured to support transmissions to/from theairborne aircraft; calculate a first forward-link user capacity estimateusing the first signal-to-noise ratio of the first communicationchannel; calculate a second forward-link user capacity estimate usingthe second signal-to-noise ratio of the second communication channel;and calculate a forward-link user capacity matrix using the firstforward-link user capacity estimate and the second forward-link usercapacity estimate, wherein the forward-link user capacity matrix isutilized to select communication channels to utilize for transmissionsbetween a plurality of ground stations disposed on the ground and theairborne aircraft.
 2. The medium of claim 1, wherein the firstcommunication channel comprises a first center frequency and a firstbandwidth, wherein the second communication channel comprises a secondcenter frequency and a second bandwidth, and wherein the firstcommunication channel does not overlap the second communication channel.3. The medium of claim 1, wherein the processor executable instructions,when executed by the computer processor, cause the computer processorto: command the directional antenna and the transceiver to measure ashort-term average of the first signal-to-noise ratio of the firstcommunication channel; command the directional antenna and thetransceiver to measure a short-term average of the secondsignal-to-noise ratio of the second communication channel; calculate thefirst forward-link user capacity estimate using the short-term averageof the first signal-to-noise ratio of the first communication channel;and calculate the second forward-link user capacity estimate using theshort-term average of the second signal-to-noise ratio of the secondcommunication channel.
 4. The medium of claim 1, wherein the processorexecutable instructions, when executed by the computer processor, causethe computer processor to: command the directional antenna and thetransceiver to measure a long-term average of the first signal-to-noiseratio of the first communication channel; command the directionalantenna and the transceiver to measure a long-term average of the secondsignal-to-noise ratio of the second communication channel; calculate thefirst forward-link user capacity estimate using the long-term average ofthe first signal-to-noise ratio of the first communication channel; andcalculate the second forward-link user capacity estimate using thelong-term average of the second signal-to-noise ratio of the secondcommunication channel.
 5. The medium of claim 1, further comprisingadditional processor executable instructions that when executed by thecomputer processor cause the computer processor to command thedirectional antenna and the transceiver to transmit the forward-linkuser capacity matrix to a ground station controller using an out-of-bandcommunication channel, the ground station controller disposed on theground and in communicative connection with the plurality of groundstations.
 6. The medium of claim 1, further comprising additionalprocessor executable instructions that when executed by the computerprocessor cause the computer processor to: command the directionalantenna and the transceiver to measure a third signal-to-noise ratio ofa third communication channel corresponding to a third location on theground, the third communication channel configured to supporttransmissions to/from the airborne aircraft; calculate a thirdforward-link user capacity estimate using the third signal-to-noiseratio of the third communication channel; and calculate the forward-linkuser capacity matrix using the first forward-link user capacityestimate, the second forward-link user capacity estimate, and the thirdforward-link user capacity estimate.
 7. A computer-implemented method,executed with a computer processor disposed within an air-to-groundcommunication ground station, comprising: commanding, with the computerprocessor, a directional antenna installed at the ground station and atransceiver disposed within the ground station to measure a first noisepower level of a first communication channel at a first elevation and afirst azimuth from a current position of the ground station, the firstcommunication channel configured to support transmissions between theground station and airborne aircraft; commanding, with the computerprocessor, the directional antenna and the transceiver to measure asecond noise power level of a second communication channel at a secondelevation and a second azimuth from the current position of the groundstation, the second communication channel configured to supporttransmissions between the ground station and the airborne aircraft;calculating, with the computer processor, a first reverse-link noiseestimate using the first noise power level of the first communicationchannel; calculating, with the computer processor, a second reverse-linknoise estimate using the second noise power level of the secondcommunication channel; and calculating, with the computer processor, areverse-link noise matrix using the first reverse-link noise estimateand the second reverse-link noise estimate, wherein the reverse-linknoise matrix is utilized to select communication channels to utilize fortransmissions between a plurality of ground stations disposed on theground and the airborne aircraft.
 8. The method of claim 7, wherein thefirst communication channel comprises a first center frequency and afirst bandwidth, wherein the second communication channel comprises asecond center frequency and a second bandwidth, and wherein the firstcommunication channel does not overlap the second communication channel.9. The method of claim 7, further comprising: commanding, with thecomputer processor, the directional antenna and the transceiver tomeasure a short-term average of the first noise power level of the firstcommunication channel at the first elevation and the first azimuth;commanding, with the computer processor, the directional antenna and thetransceiver to measure a short-term average of the second noise powerlevel of the second communication channel at the second elevation andthe second azimuth; calculating, with the computer processor, the firstreverse-link noise estimate using the short-term average of the firstnoise power level of the first communication channel; and calculating,with the computer processor, the second reverse-link noise estimateusing the short-term average of the second noise power level of thesecond communication channel.
 10. The method of claim 7, furthercomprising: commanding, with the computer processor, the directionalantenna and the transceiver to measure a long-term average of the firstnoise power level of the first communication channel at the firstelevation and the first azimuth; commanding, with the computerprocessor, the directional antenna and the transceiver to measure along-term average of the second noise power level of the secondcommunication channel at the second elevation and the second azimuth;calculating, with the computer processor, the first reverse-link noiseestimate using the long-term average of the first noise power level ofthe first communication channel; and calculating, with the computerprocessor, the second reverse-link noise estimate using the long-termaverage of the second noise power level of the second communicationchannel.
 11. The method of claim 7, further comprising commanding, withthe computer processor, the ground station to transmit the reverse-linknoise matrix to a ground station controller, the ground stationcontroller disposed on the ground and in communicative connection withthe plurality of ground stations.
 12. The method of claim 7, furthercomprising: commanding, with the computer processor, the directionalantenna and the transceiver to measure a third noise power level of athird communication channel at a third elevation and a third azimuthfrom the current position of the ground station, the third communicationchannel configured to support transmissions between the ground stationand airborne aircraft; calculating, with the computer processor, a thirdreverse-link noise estimate using the third noise power level of thethird communication channel; and calculating, with the computerprocessor, the reverse-link noise matrix using the first reverse-linknoise estimate, the second reverse-link noise estimate, and the thirdreverse-link noise matrix.
 13. A computer system comprising one or moreprocessors and/or transceivers configured to: retrieve at least one of:(i) a forward-link user capacity matrix comprising a plurality offorward-link user capacity estimates each associated with a respectivesignal-to-noise ratio measurement of a respective communication channelcorresponding to a respective location on the ground; or (ii) areturn-link user capacity matrix comprising a plurality of return-linkuser capacity estimates each associated with a respective noise powerlevel of a respective communication channel corresponding to arespective azimuth and a respective elevation from a current location ofan airborne aircraft; determine, using at least one of (i) theforward-link user capacity matrix or (ii) the return-link user capacitymatrix, a candidate serving cell that is disposed on the ground; andcommand a directional antenna and a particular transceiver to transmitor receive data between the airborne aircraft and the candidate servingcell.
 14. The system of claim 13, wherein the one or more processorsand/or transceivers are configured to retrieve the at least one of (i)the forward-link user capacity matrix or (ii) the return-link usercapacity matrix from an air-to-ground network controller disposed on theground and in communicative with a plurality of serving cells, theplurality of serving cells including the candidate serving cell.
 15. Thesystem of claim 13, wherein the candidate serving cell comprises arespective noise power level above a threshold.
 16. The system of claim13, wherein the one or more processors and/or transceivers are furtherconfigured to transmit the at least one of (i) the forward-link usercapacity matrix or (ii) the return-link user capacity matrix using anout-of-band channel.
 17. The system of claim 13, wherein theforward-link user capacity matrix indicates a lower signal-to-noiseratio associated with the candidate serving cell than an alternativeserving cell, and wherein the alternative serving cell is located at adistance from the airborne aircraft that is greater than a distance fromthe airborne aircraft of the candidate serving cell.
 18. The system ofclaim 13, wherein the return-link user capacity matrix indicates ahigher noise power level associated with the candidate serving cell thana noise power level associated with an alternative serving cell, andwherein the alternative serving cell is located at a distance from theairborne aircraft that is greater than a distance from the airborneaircraft of the candidate serving cell.
 19. The system of claim 15,wherein the threshold comprises at least one of: a short-term noisethreshold that enables a serving cell selection decision among aplurality of serving cells; or a long-term noise threshold that enablesa future serving cell restriction decision.